This application claims the priority of German patent 197 18 618.1-33, filed on May 2, 1997 in Germany, the disclosure of which is expressly incorporated by reference herein.
The invention relates to a composite structure with a growth substrate having several microelectronic devices and a diamond layer and a method for producing the composite structure.
DE 44 27 715 C1 teaches a method for producing a composite substrate in which a diamond layer is initially deposited directly on a growth substrate. A semiconductor layer is then placed on the diamond layer. Several microelectronic devices are then placed on the semiconductor layer or with the functional assistance of the semiconductor layer. The devices are to be construed as individual devices such as diodes, transistors, capacitors, inductances, etc. but also include device groups such as integrated circuits (ICs), amplifiers, storage devices, etc. As the semiconductor layer grows, the number of impurities under the devices, namely in the area of the device root, is reduced. The diamond layer has edges outside the device roots. On these edges located between the devices, and on which the diamond layer is thinner than in the vicinity of the device roots, the quality of the semiconductor layer deposited subsequently is improved above the diamond layer. Because of this improvement in semiconductor layer quality, at least in the area of the device roots, the rejection rate in production of the devices is reduced. After the epitactic production of the devices, known of itself, and their subsequent provision with contacts, the devices are then separated from each other in particular by sawing, with the growth substrate being removed by selective etching before or even after separation. Despite this improvement, the rejection rate is still high, so that these devices are still very expensive. Moreover, manufacture of a diamond layer with such edges is technologically difficult and hence is expensive as well.
The goal of the invention is to improve the composite structure so that the total costs for microelectronic devices made with the aid of the composite structure are reduced, with the best possible device quality.
This goal is achieved according to the present invention. Despite the high temperature that endangers devices when polycrystalline diamond is deposited on devices that are already finished and produced directly in known fashion, the rejection rate is reduced. Thus, the total costs of producing the devices is reduced. Moreover, the method of manufacturing the devices is known and can be accomplished at very low cost; the same applies to deposition of the diamond layer, as attention no longer needs be paid to its structure (edges). In particular, the devices can continue to be separated by sawing up the composite structure, and the diamond layer applied to most of the devices is still usable after sawing.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.